| #/*++ | |
| # | |
| #Copyright (c) 2006, Intel Corporation. All rights reserved.<BR> | |
| #This program and the accompanying materials | |
| #are licensed and made available under the terms and conditions of the BSD License | |
| #which accompanies this distribution. The full text of the license may be found at | |
| #http://opensource.org/licenses/bsd-license.php | |
| # | |
| #THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, | |
| #WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. | |
| # | |
| #Module Name: | |
| # | |
| # Log2.c | |
| # | |
| #Abstract: | |
| # | |
| # 64-bit integer logarithm function for IA-32 | |
| # | |
| #--*/ | |
| # | |
| #--------------------------------------------------------------------------- | |
| #include "EfiBind.h" //For ASM_PFX | |
| #--------------------------------------------------------------------------- | |
| .globl ASM_PFX(Log2) | |
| #UINT8 | |
| #Log2 ( | |
| # IN UINT64 Operand | |
| # ) | |
| #/*++ | |
| # | |
| #Routine Description: | |
| # | |
| # Calculates and floors logarithms based on 2 | |
| # | |
| #Arguments: | |
| # | |
| # Operand - value to calculate logarithm | |
| # | |
| #Returns: | |
| # | |
| # The largest integer that is less than or equal | |
| # to the logarithm of Operand based on 2 | |
| # | |
| #--*/ | |
| ASM_PFX(Log2): | |
| movl $64, %ecx | |
| cmpl $0, 4(%esp) # (UINT32 *(&Operand)) | |
| jne _Log2_Wend | |
| cmpl $0, 8(%esp) # (UINT32 *(&Operand)) + 1 | |
| jne _Log2_Wend | |
| movb $0xFF, %cl | |
| jmp _Log2_Done | |
| _Log2_Wend: | |
| decl %ecx | |
| cmpl $32, %ecx | |
| jae _Log2_Higher | |
| btl %ecx, 4(%esp) # (UINT32 *(&Operand)) | |
| jmp _Log2_Bit | |
| _Log2_Higher: | |
| movl %ecx, %eax | |
| subl $32, %eax | |
| btl %eax, 8(%esp) # (UINT32 *(&Operand)) + 1 | |
| _Log2_Bit: | |
| jc _Log2_Done | |
| jmp _Log2_Wend | |
| _Log2_Done: | |
| movb %cl, %al | |
| ret | |